Short wave radiation



Sept. 22, 1936.

w. DALLENBACH 2,054,895

SHORT WAVE RADIATION Filed June 26, 1953 /n ventor: W- d g'lll -finbalc/h Patented se t. 22,1936 v v 2,054,895

UNITED STATES PATENT OFFICE 2.054.895 snon'r WAVE RADIATION WalterDillenbach, Berlin-Charlottenburg, Germany, assignor to N. V.Machinerieen-en Appar'aten Fabrieken "Meat", Utrecht, NetherlandsApplication June 26, 1933, Serial No. 847,733 Infiermany July 6, 1932Claims. (Cl. 250-11) It is difficult when communicating with ultrain theaccompanying drawing, in which Figures short waves to cause sender andreceiver to oper- 1, 2 and 3 are diagrams of embodiments of ateselectively so that neither an undesired rethe invention. I ception offoreign stations by one's own re- Fig. 1 shows an arrangement having anelec- 5 ceiver nor the unauthorized reception of one's tric dipolerepresented by the linear oscillator ST 5 own transmissions by thirdpersons or'their inwhich coincides with the axis X-X of a.paraterl'erence is possible. In order to obtain high bolic mirrorhaving coinciding axes of rotation selectivity it has been proposed tosend the sender and symmetry, the focus of the mirror being at F on avery narrow and constant wave band and and the apex at A. The directionof propagation to provide the receiver with the best possible of therays emitted by the mirror also coincides l0 screening means. with thedirection X-X and thus with the axis of In order to render messagesinaccessible to unthe linear oscillator ST. authorized persons duringthe transmission of in- Such an arrangement produces radiation whichtelligence, it has been proposed to build senders differs in essentialpoints from the known arfor a very narrow wave range and thus makerangements for producing directional waves, and 15 reception moredifiicult. Furthermore, arrangefurther explanation will be given withreference ments have been proposed which, as far as posto the exampleshown in Fig. 1. Corresponding sible, permit the bunching together ofthe rays to the direction diagram of the emitter indiin one direction toprevent, or render difiicult, cated, the radiated energy will preferablybe reception in other directions, but such arrangeemitted in theequatorial plane MNF while only 20 ments fail to give satisfaction inview of the invery slight portions of the rays will fall into thecreasing use of receiving devices. angular space PFQ where the radiationleaves the By producing a wave of peculiar structure the mirror withoutbeing reflected and concentrated. invention provides a means forrendering recep- This means that stray radiation falling, in the 5 tionby unauthorized persons extraordinarily usual arrangements, in theangular space PFQ difficult, is practically eliminated in thearrangement ac- An electromagnetic oscillator, such as an eleccording toFig. 1, which produces greater concentric or magnetic dipole, has anaxis of symmetry tration of the rays in the interest of secrecy and inwhich it practically does not radiate at all. in order to avoidinterference with adjacent sta- The rays emitted by it extend chieflyvertically tions. Simultaneously, the new arrangement 30 to the axis inthe equatorial plane and decrease makes it possible to reflectpractically the entire in the direction towards the pole in the squareradiated energy emitted by the sender ST on the of the cosine of thegeographical latitude. To mirror in the direction XX, which involves apermit utilization ofthe directional radiation, an considerable savingin expenditure of energy or emitter of this type has always beenarranged so a higher field intensity at the point of reception. 35 thatits axis was adjusted vertically to the direc- However, the newarrangement affords another tionof propagation into which the rays wereto advantage. The energy emitted by the radiator be thrown. In wirelesstelegraphy, the axis of leaves the mirror without passing over theradisymmetry of an aerial is, therefore, as a rule, ator again, as isalways the case with arrangeoriented vertically to the earths surface.Ultraments in which the emitter is disposed vertically 4') shortelectric waves in the sphere of centimeter to, the mirror axis. In anarrangement of the and decimeter waves permit concentration of hithertocustomary type a coupling will thereradiation for instance by means ofreflectors. fore be produced between the mirror and emitter, Applyingthe fundamental principle mentioned which makes it necessary to choosethe focal disabove, when such reflectors were used, the artance of themirror at a certain ratio to the wave rangement of the axis of symmetryof the emitter length, whereas in the arrangement shownin relative tothe direction of' propagation of the Fig. 1 such a coupling betweenreflectors and rays has been retained, so that even in case of aemitters is not required, so that the focal disreflector, the axis ofsymmetry is adjusted vertance ofthe mirror may be chosen independently5o tically to the direction of propagation. from the wave length. 5 Ithas been found, however, that an essential The new arrangement furtherpossesses a speadvance may be made by arranging the axis of cial featureby supplying a ray of a certain strucsymmetry of the emitter in adifferent way if a ture, The intensity of radiation is greatest on areflector is used. cylindrical face having the axis X-X and the By wayof example, the invention is illustrated circle above the diameter MN'ascross section, 55

' ray to be received possesses and radially decreases from this surfaceboth outwardly and inwardly. The magnetic lines of force are circlesabout the axis X-X, but the electric lines of force extend as crosssectional lines of torus faces which also have the axis of symmetry X-Xfor their axis of'rotation. In Fig. 3, this is shown in perspecti thegeneral arrangement being the same as in Fig. 1. The points of greatestintensity of radiation are located on the circular cylinder'constructedabove the diameter MN with the axis X-X. A section made vertically tothe axis of this circular cylinder represents a magnetic line of forceH. The intensity of the magnetic field strength along such a line offorce H varies for a certain length of time periodically in thedirection of the axis X-X in so far as the field strength, dropping frommaximum to zero, attains after half a wave length the maximum value inopposite direction. The electric field strength for points near thecircular cylinder of maximum'intensity of radiation is chiefly radiallydirected, i. e., in distances length with maximum intensity oroutwardly. At distances amounting to a few wave lengths from the crosssectional surface MN the 'maxima of magnetic field strength willcoincide with the maxima of electric field strength. Magnetic andelectric field strengths are, therefore, arranged relative to oneanother as indicated by the vectors E and H. Vertically to the latterthe vector U of the energy flow points in the direction X-X, so that theelectric lines of force extend in the meridional planes through the axisx-x and form closed curves K, as indicated for the meridional plane bythe point M.

The novel arrangement of the emitter relative to themirror thus permitsthe formation of a tube-like ray which possess the advantage ofextremely sharp concentration and which permits reception by anotherstation only if transmitting and receiving stations are accuratelyadjusted to one another.

It is evident that the effect described can be attained also in a mannerdiffering from the arrangement according to Fig. 1. For example, Fig. 2shows an arrangement in which the electric dipole is replaced byamagnetic dipole in the form of a circular conductor disposed in thefocus coaxially with the mirror and traversed by a high frequencycurrent. This arrangement shows the lines of force disposed in a mannercoinciding with that of Fig. 3, provided the magnetic lines of force aresubstituted for the electric lines.

The arrangement described in connection with a transmitter can be usedalso for a mirror system intended for reception, provided that the thetube-like form mentioned above, since only in this case will an emitteradjusted with its axis of symmetry to the direction of propagationrespond. The formation of the beam according to the invention comparedwith an ordinary plane may therefore be likened to a safety key whilethe plane wave represents an ordinary key. The highly complicatedstructure of the beam compared with a plane wave requires acorresponding adaptation of the reception to the transmitted wave andthus protectsthe receiving station to a very high degree againstresponding due to any electromagnetic interferences of other kinds, sothat reception is rendered free from interferences.

Rays of the kind described are particularly suited also for electrictrain protection.

work requiring great accuracy,

findings for fixing routes for aircraft and hydro- 8 of symmetry of thereflector,

aosascs Furthermore, the use of structured electromagnetic rays withaxis of rotation or a plane of sym metry is advisable also for allposition finding such as direction aeroplanes or the like.

Theemitters disposed in the mirror may be tubes or serials connectedwith tubes by high frequency circuits. Instead of a parabolic mirrorhaving coinciding axes of metry a cylindrical mirror disclosing aparabola in cross section may be employed. If in this arrangement theaxis of the dipole is disposed again in the direction of propagation ofthe ray coming from the mirror, the wave leaving the mirror is no 15longer rotation-symmetrical but. has a plane of symmetry, 1. e., theplane determined by the parabola and the direction of the surface linesof the cylinder.

In the customary arrangement, for instance, 20

the axis of the electric dipole is disposed vertically in the focus of aparabolic mirror adjusted with horizontal axis. The beam leaving themirror is then, over the entire cross section, approximately linearlypolarized in such a way that at 25 all points of the cross section ofthe beam the electric field strength is directed approximatelyvertically and the magnetic field strength approximately horizontally,so that the beam corresponds accurately to a space.

0n the other hand, if, according to the invention, the axis of thedipole lies in the axis of the parabolic mirror, that is, is disposed inthe direction of propagation of the ray, a tube-like ray 35 will beproduced which completely deviates from the plane wave. It is asimpossible to change the structure of this ray to that of a plane waveby steady transformation as it is to convert a torus surface to aspherical one by steady deformation.

If instead of a parabolic mirror having coinciding axes of symmetry androtation a parabolic mirror is chosen whose cross section, vertically tothe axis of symmetry, will produce an ellipse, the cross section of thetubular ray will also be elliptically deformed and, if the major axis ofthe elliptical cross section is extended to infinity, pass into the fallof the ray with the axis of symmetry.

I claim:

1. A system for the transmission of messages by short electric waves,consisting of a sender and a receiver, the sender .comprising arotarysymmetrical reflector and an electric dipole, the receivercomprising a rotary-symmetrical refiector and an electric dipole, eachdipole arranged in the focus of the associated reflector and extend ingin the direction of the axis of the reflector, whereby the senderproduces a tubular parallel radiation field, the receiver receiving thistubular radiation field.

2. A system for the transmission of messages by short electric waves,consisting of a sender and a receiver, the sender comprising arotarysymmetrical reflector anda magnetic dipole, the receivercomprising a rotary-symmetrical reflector and a magnetic dipole, eachmagnetic dipole arranged in the focus of the associated reflector andits axis of symmetry coinciding with the axis whereby the senderproduces a tubularradiation field, the receiver receiving this tubularradiation field. V

3. A system for transmitting messages with short electric waves,consisting of a sender and a receiventhe sender containing a rotary-sym-1 rotation and syml0 plane wave limited as to 30 metrical reflector anda dipole, the receiver conup by the receiver practically over its entirecross taming a rotary-symmetrical reflector and a disection. pole, eachdipole being disposed in the focal point 5. A system for transmittingmessages through of the associated reflector, and its axis of synrshortelectric waves, consisting of a sender and a metry coinciding with theaxis of symmetry of receiver, the sender comprising a reflector and an sthe reflector, whereby the sender generates a oscillator, the receivercomprising a reflector cortubular parallel radiating field, the receiverreresponding to the reflector of the sender and an ceives this tubularradiatinrfield. oscillator, which is disposed in the reflector of 4. Asystem for transmitting messages through the receiver in the sameposition as the oscillator short electric waves, consisting of a senderand a of the Sender n he eflecto 0f the S d each 10 receiver, the sendercomprising a reflector and an oscillator dispos d in e focal P i f hoscillator, the receiver comprising a reflector corflector, its axiscoinciding with the direction of responding to the reflector of thesender and an the m tt d a t n. wh y th nd r pr oscillator, eachoscillator disposed in the focal duces anon-homogeneous, parallelradiation field point of the reflector, its axis coinciding with the andsubstantially the entire cross section of the 145 direction 01 theemitted radiation, whereby the m e a i n m is taken p y th receiversender produces a non-homogeneous parallel practically over its entirecross section. radiation field and substantially the entire crosssection of the emitted radiation beam is taken WALTER DALLENBAOH.

